Ion transport membrane module and vessel system

ABSTRACT

An ion transport membrane system comprising (a) a pressure vessel having an interior, an exterior, an inlet, and an outlet; (b) a plurality of planar ion transport membrane modules disposed in the interior of the pressure vessel and arranged in series, each membrane module comprising mixed metal oxide ceramic material and having an interior region and an exterior region, wherein any inlet and any outlet of the pressure vessel are in flow communication with exterior regions of the membrane modules; and (c) one or more gas manifolds in flow communication with interior regions of the membrane modules and with the exterior of the pressure vessel. 
     The ion transport membrane system may be utilized in a gas separation device to recover oxygen from an oxygen-containing gas or as an oxidation reactor to oxidize compounds in a feed gas stream by oxygen permeated through the mixed metal oxide ceramic material of the membrane modules.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under DOE CooperativeAgreement No. DE-FC26-98FT40343 between Air Products and Chemicals,Inc., and the United States Department of Energy. The Government hascertain rights to this invention.

BACKGROUND OF THE INVENTION

The permeation of oxygen ions through ceramic ion transport membranes isthe basis for a variety of gas separation devices and oxidation reactorsystems operating at high temperatures in which permeated oxygen isrecovered on the permeate side as a high purity oxygen product or isreacted on the permeate side with oxidizable compounds to form oxidizedor partially oxidized products. The practical application of these gasseparation devices and oxidation reactor systems requires membraneassemblies having large surface areas, means to contact feed gas withthe feed sides of the membranes, and means to withdraw product gas fromthe permeate sides of the membranes. These membrane assemblies maycomprise a large number of individual membranes arranged and assembledinto modules having appropriate gas flow piping to introduce feed gasinto the modules and withdraw product gas from the modules.

Ion transport membranes may be fabricated in either planar or tubularconfigurations. In the planar configuration, multiple flat ceramicplates are fabricated and assembled into stacks or modules having pipingmeans to pass feed gas over the planar membranes and to withdraw productgas from the permeate side of the planar membranes. In tubularconfigurations, multiple ceramic tubes may be arranged in bayonet orshell-and-tube configurations with appropriate tube sheet assemblies toisolate the feed and permeate sides of the multiple tubes.

The individual membranes used in planar or tubular module configurationstypically comprise very thin layers of active membrane materialsupported on material having large pores or channels that allow gas flowto and from the surfaces of the active membrane layers. The ceramicmembrane material and the components of the membrane modules can besubjected to significant mechanical stresses during normal steady-stateoperation and especially during unsteady-state startup, shutdown, andupset conditions. These stresses may be caused by thermal expansion andcontraction of the ceramic material and by dimensional variance causedby chemical composition or crystal structure changes due to changes inthe oxygen stoichiometry of the membrane material. These modules mayoperate with significant pressure differentials across the membrane andmembrane seals, and stresses caused by these pressure differentials mustbe taken into account in membrane module design. In addition, therelative importance of these phenomena may differ depending on whetherthe modules are operated in gas separation or oxidation service. Thepotential operating problems caused by these phenomena may have asignificant negative impact on the purity of recovered products and onmembrane operating life.

There is a need in the field of high temperature ceramic membranereactor systems for new membrane module and vessel designs that addressand overcome these potential operating problems. Such designs shouldinclude features to allow efficient operation, long membrane life,minimum capital cost, and the ability to specify membrane systems over awide range of production rates. Embodiments of the invention disclosedherein address these design problems and include improved module andvessel designs for both oxygen production and oxidation systems.

BRIEF SUMMARY OF THE INVENTION

An embodiment of the invention relates to an ion transport membranesystem comprising a pressure vessel having an interior, an exterior, aninlet, and an outlet; a plurality of planar ion transport membranemodules disposed in the interior of the pressure vessel and arranged inseries, each membrane module comprising mixed metal oxide ceramicmaterial and having an interior region and an exterior region, whereinany inlet and any outlet of the pressure vessel are in flowcommunication with exterior regions of the membrane modules; and one ormore gas manifolds in flow communication with interior regions of themembrane modules and with the exterior of the pressure vessel.

Each planar membrane module typically comprises a plurality of wafershaving planar parallel surfaces; the pressure vessel may be cylindricaland may have an axis that is parallel to some or all of the planarparallel surfaces of the wafers.

The system may further comprise a flow containment duct disposed in theinterior of the pressure vessel, wherein the flow containment ductsurrounds the plurality of planar ion transport membrane modules and isin flow communication with any inlet and any outlet of the pressurevessel. The one or more gas manifolds may comprise an inlet manifold andan outlet manifold; the interior region of any planar membrane modulemay be in flow communication with the inlet manifold via a secondaryinlet manifold and may be in flow communication with the outlet manifoldvia a primary outlet manifold; and within the flow containment duct, thesecondary inlet manifold and the primary outlet manifold of any planarmembrane module may be combined to form a nested manifold. The flowcontainment duct may comprise an oxidation-resistant metal alloycontaining iron and one or more elements selected from the groupconsisting of nickel and chromium.

The one or more gas manifolds may be disposed in the interior of thepressure vessel or exterior to the pressure vessel. The one or more gasmanifolds may be insulated internally, externally, or internally andexternally.

At least two of the planar ion transport membrane modules define amodule axis, wherein the pressure vessel may be cylindrical and may havean axis that is parallel to the module axis. At least two of the planarion transport membrane modules may define a module axis, wherein thepressure vessel may be cylindrical and may have an axis that isperpendicular to the module axis.

The system may further comprise insulation disposed in the interior ofthe pressure vessel. The insulation may be disposed in a region betweenan interior surface of the pressure vessel and the membrane modules,wherein the insulation forms a cavity that surrounds the membranemodules and the cavity is in flow communication with any inlet and anyoutlet of the pressure vessel. Alternatively, the insulation may be incontact with the interior surface of the pressure vessel. In anotheralternative, the insulation may not be not in contact with the interiorsurface of the pressure vessel. In yet another alternative, the systemmay further comprise a flow containment duct disposed in the interior ofthe pressure vessel, wherein the planar ion transport membrane modulesare disposed within the duct, and wherein the insulation is disposedbetween an interior surface of the pressure vessel and an exteriorsurface of the duct.

The insulation may (a) be in contact with the interior surface of thepressure vessel and is not in contact with the exterior surface of theduct; (b) be in contact with the interior surface of the pressure vesseland is in contact with the exterior surface of the duct; (c) not be incontact with the interior surface of the pressure vessel and not be incontact with the exterior surface of the duct; or (d) not be in contactwith the interior surface of the pressure vessel and be in contact withthe exterior surface of the duct.

The system may further comprise a flow containment duct disposed in theinterior of the pressure vessel and in flow communication with the inletand outlet of the pressure vessel, wherein the planar ion transportmembrane modules are disposed within the duct, wherein the insulation isdisposed between an interior surface of the duct and the membranemodules, and wherein the insulation forms a cavity that surrounds themembrane modules and is in flow communication with any inlet and anyoutlet of the pressure vessel. The system may further compriseinsulation around the exterior of the pressure vessel.

The one or more gas manifolds may comprise metal and the ion transportmodules may comprise ceramic, wherein connections between the one ormore gas manifolds and the modules may include ceramic-to-metal seals,and wherein the ceramic-to-metal seals may be surrounded by theinsulation.

The insulation may comprise one or more materials selected from thegroup consisting of fibrous alumina, fibrous alumina silicate, porousalumina, porous alumina silicate. The insulation may comprise one ormore materials selected from the group consisting of magnesium oxide,calcium oxide, copper oxide, calcium carbonate, sodium carbonate,strontium carbonate, zinc oxide, strontium oxide, andalkaline-earth-containing perovskites.

The system may further comprise a guard bed disposed between any inletof the pressure vessel and a first membrane module. This guard bed maycontain one or more materials selected from the group consisting ofmagnesium oxide, calcium oxide, copper oxide, calcium carbonate, sodiumcarbonate, strontium carbonate, zinc oxide, strontium oxide, andalkaline-earth-containing perovskites.

The ion transport membrane system may further comprise

-   -   (a) one or more additional pressure vessels, each having an        interior, an exterior, an inlet, and an outlet;    -   (b) a plurality of planar ion transport membrane modules        disposed in the interior of each of the one or more pressure        vessels and arranged in series, each membrane module comprising        mixed metal oxide ceramic material and having an interior region        and an exterior region, wherein any inlet and any outlet of the        pressure vessel are in flow communication with exterior regions        of the membrane modules; and    -   (c) one or more gas manifolds in flow communication with        interior regions of the membrane modules and with the exterior        of the pressure vessel;        wherein at least two of the pressure vessels are arranged in        series such that the outlet of one pressure vessel is in flow        communication with the inlet of another pressure vessel.

Alternatively, the ion transport membrane system may further comprise

-   -   (a) one or more additional pressure vessels, each having an        interior, an exterior, an inlet, and an outlet;    -   (b) a plurality of planar ion transport membrane modules        disposed in the interior of each of the one or more pressure        vessels and arranged in series, each membrane module comprising        mixed metal oxide ceramic material and having an interior region        and an exterior region, wherein any inlet and any outlet of the        pressure vessel are in flow communication with exterior regions        of the membrane modules; and    -   (c) one or more gas manifolds in flow communication with the        interior regions of the membrane modules and with the exterior        of the pressure vessel;        wherein at least two of the pressure vessels are arranged in        parallel such that any inlet of one pressure vessel and any        inlet of another pressure vessel are in flow communication with        a common feed conduit.

The system may further comprise an additional plurality of planar iontransport membrane modules disposed in the interior of the pressurevessel and arranged in series, wherein the plurality of planar iontransport membrane modules and the additional plurality of planar iontransport membrane modules lie on parallel axes.

A further embodiment if the invention is an ion transport membranesystem comprising

-   -   (a) a pressure vessel having an interior, an exterior, an inlet,        and an outlet;    -   (b) a plurality of planar ion transport membrane modules        disposed in the interior of the pressure vessel and arranged in        a series of banks of modules, each bank containing two or more        modules in parallel, each membrane module comprising mixed metal        oxide ceramic material and having an interior region and an        exterior region, wherein any inlet and any outlet of the        pressure vessel are in flow communication with exterior regions        of the membrane modules; and    -   (c) one or more gas manifolds in flow communication with        interior regions of the membrane modules and with the exterior        of the pressure vessel.

An alternative embodiment of the invention is an ion transport membranesystem comprising

-   -   (a) a pressure vessel having an interior, an exterior, an inlet,        and an outlet;    -   (b) a plurality of ion transport membrane modules disposed in        the interior of the pressure vessel and arranged in series, each        membrane module comprising mixed metal oxide ceramic material        and having an interior region and an exterior region, wherein        any inlet and any outlet of the pressure vessel are in flow        communication with exterior regions of the membrane modules; and    -   (c) one or more gas manifolds disposed in the interior of the        pressure vessel and in flow communication with the interior        regions of the membrane modules and with the exterior of the        pressure vessel.

Another alternative embodiment of the invention is an ion transportmembrane system comprising

-   -   (a) a pressure vessel having an interior, an exterior, an inlet,        and an outlet;    -   (b) a membrane stack or module assembly disposed in the interior        of the pressure vessel, the assembly having a plurality of        planar wafers comprising mixed metal oxide ceramic material,        each wafer having an interior region and an exterior region, and        a plurality of hollow ceramic spacers, wherein the stack or        module assembly is formed by alternating wafers and spacers such        that the interiors of the wafers are in flow communication via        the hollow spacers, the wafers are oriented parallel to one        another, and the alternating spacers and wafers are oriented        coaxially to form the stack or module such that the wafers are        perpendicular to the stack or module axis;    -   (c) a gas manifold shroud assembly disposed around the membrane        stack or module assembly within the interior of the pressure        vessel, wherein the shroud assembly separates the stack or        module into at least a first wafer zone and a second wafer zone,        places any inlet of the pressure vessel in flow communication        with exterior regions of the wafers in the first wafer zone, and        places exterior regions of the wafers in the first wafer zone in        series flow communication with exterior regions of the wafers of        the second wafer zone.

This ion transport membrane system may further comprise a plurality ofadditional wafer zones formed by the gas manifold shroud assembly,wherein the shroud assembly places the additional wafer zones in seriesflow communication with one another, and wherein one of the additionalwafer zones is in flow communication with any outlet of the pressurevessel.

Another embodiment of the invention includes a method for the recoveryof oxygen from an oxygen-containing gas comprising

-   -   (a) providing an ion transport membrane separator system        comprising        -   (1) a pressure vessel having an interior, an exterior, an            inlet, and an outlet;        -   (2) a plurality of planar ion transport membrane modules            disposed in the interior of the pressure vessel and arranged            in series, each membrane module comprising mixed metal oxide            ceramic material and having an interior region and an            exterior region, wherein any inlet and any outlet of the            pressure vessel are in flow communication with exterior            regions of the membrane modules; and        -   (3) one or more gas manifolds in flow communication with the            interior regions of the membrane modules and with the            exterior of the pressure vessel;    -   (b) providing a heated, pressurized oxygen-containing feed gas        stream, introducing the feed gas stream via any pressure vessel        inlet to the exterior regions of the membrane modules, and        contacting the feed gas stream with the mixed metal oxide        ceramic material;    -   (c) permeating oxygen ions through the mixed metal oxide ceramic        material, recovering high purity oxygen gas product in the        interior regions of the membrane modules, and withdrawing the        high purity oxygen gas product from the interior regions of the        membrane modules through the gas manifolds to the exterior of        the pressure vessel; and    -   (d) withdrawing an oxygen-depleted oxygen-containing gas from        any pressure vessel outlet.

The pressure of the oxygen-containing feed gas typically is greater thanthe pressure of the high purity oxygen gas product. The ion transportmembrane separator system further may comprise a flow containment ductthat has an interior and an exterior and is disposed in the interior ofthe pressure vessel, and wherein the flow containment duct surrounds theplurality of planar ion transport membrane modules and is in flowcommunication with any inlet and any outlet of the pressure vessel suchthat the oxygen-containing feed gas passes through the interior of theflow containment duct.

The pressure differential between the interior and the exterior of theflow containment duct at any point between the inlet and outlet of thepressure vessel may be maintained at a value equal to or greater thanzero, wherein the pressure in the interior of the duct may be equal toor greater than the pressure in the pressure vessel exterior to theduct.

Another embodiment of the invention relates to an oxidation processcomprising

-   -   (a) providing an ion transport membrane reactor system        comprising        -   (1) a pressure vessel having an interior, an exterior, an            inlet, and an outlet;        -   (2) a plurality of planar ion transport membrane modules            disposed in the interior of the pressure vessel and arranged            in series, each membrane module comprising mixed metal oxide            ceramic material and having an interior region and an            exterior region, wherein any inlet and any outlet of the            pressure vessel are in flow communication with exterior            regions of the membrane modules; and        -   (3) one or more gas manifolds in flow communication with            interior regions of the membrane modules and with the            exterior of the pressure vessel;    -   (b) providing a heated, pressurized reactant feed gas stream,        introducing the reactant feed gas stream via any pressure vessel        inlet to the exterior regions of the membrane modules;    -   (c) providing an oxygen-containing oxidant gas to the interior        regions of the membrane modules, permeating oxygen ions through        the mixed metal oxide ceramic material, reacting oxygen with        components in the reactant feed gas stream in the exterior        regions of the membrane modules to form oxidation products        therein, and withdrawing the oxidation products from the        exterior regions of the membrane modules through any outlet to        the exterior of the pressure vessel to provide an oxidation        product stream; and    -   (d) withdrawing oxygen-depleted oxygen-containing gas from the        interior regions of the membrane modules via the one or more        manifolds to the exterior of the pressure vessel.

In this embodiment, the pressure of the pressurized reactant feed gasstream typically is greater than the pressure of the oxygen-containingoxidant gas. The ion transport membrane reactor system may furthercomprise a flow containment duct that has an interior and an exteriorand is disposed in the interior of the pressure vessel, wherein the flowcontainment duct surrounds the plurality of planar ion transportmembrane modules and is in flow communication with the inlet and theoutlet of the pressure vessel such that the pressurized reactant feedgas stream passes through the interior of the flow containment duct.

The pressure differential between the interior and the exterior of theflow containment duct at any point between the inlet and outlet of thepressure vessel may be maintained at a value equal to or greater thanzero, and the pressure in the interior of the duct may be equal to orgreater than the pressure in the pressure vessel exterior to the duct.

The pressurized reactant feed gas stream may comprise one or morehydrocarbons having one or more carbon atoms, one of which may comprisemethane. The oxidation product stream may comprise hydrogen and carbonoxides.

Another embodiment of the invention relates to an ion transport membranereactor system comprising

-   -   (a) a pressure vessel having an interior, an exterior, an inlet,        and an outlet;    -   (b) a plurality of ion transport membrane modules disposed in        the interior of the pressure vessel, wherein a first plurality        of modules are arranged in series; and    -   (c) catalyst disposed between any two membrane modules in the        first plurality of modules.        The reactor system may further comprise a second plurality of        modules arranged in series, wherein the first plurality of        modules is arranged in parallel with the second plurality of        modules.

In this reactor system, the catalyst may be disposed between any modulesthat are arranged in parallel, between any modules that are arranged inseries, or between any modules that are arranged in parallel and betweenany modules that are arranged in series. The catalyst may comprise oneor more metals or compounds containing metals selected from the groupconsisting of nickel, cobalt, platinum, gold, palladium, rhodium,ruthenium, and iron. The catalyst may be placed between a number ofmodules in series and the activity of the catalyst may vary at differentlocations between the modules in series.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic front view of a membrane wafer stack or module foruse in oxygen recovery or in oxidation processes according toembodiments of the present invention.

FIG. 2A is a side view of the membrane wafer stack or module of FIG. 1for use in oxidation processes.

FIG. 2B is a side view of the membrane wafer stack or module of FIG. 1for use in oxygen recovery.

FIG. 3A is a sectional view of a membrane wafer of FIGS. 1, 2A, and 2B.

FIG. 3B is another sectional view of the membrane wafer of FIGS. 1, 2A,and 2B.

FIG. 3C is a sectional view of an alternative membrane wafer of FIGS. 1,2A, and 2B.

FIG. 3D is another sectional view of the alternative membrane wafer ofFIGS. 1, 2A, and 2B.

FIG. 4A is a schematic side view of the interior of a membrane separatorvessel for use in oxygen recovery.

FIG. 4B is a cross sectional view of FIG. 4A.

FIG. 5 is a schematic side view of the interior of a membrane reactorvessel for use in oxidation processes.

FIG. 6 is a cross sectional view of FIG. 5.

FIG. 7 is an embodiment of FIG. 4B showing the placement of insulationmaterial.

FIG. 8 is a second embodiment of FIG. 4B showing an alternativeplacement of thermal insulation material.

FIG. 9 is a third embodiment of FIG. 4B showing an alternative placementof thermal insulation material.

FIG. 10 is a fourth embodiment of FIG. 4B showing an alternativeplacement of thermal insulation material.

FIG. 11 is a fifth embodiment of FIG. 4B showing an alternativeplacement of thermal insulation material.

FIG. 12 is a sixth embodiment of FIG. 4B showing an alternativeplacement of thermal insulation material.

FIG. 13 is a seventh embodiment of FIG. 4B showing the placement ofinsulation thermal material.

FIG. 14 is a schematic side view of the interior of an alternativemembrane vessel and module arrangement for use in oxygen recovery or inoxidation processes.

FIG. 15 is a sectional plan view of a flow containment duct in FIG. 4Ahaving coaxial parallel membrane modules.

FIG. 16 is a sectional plan view of a flow containment duct with offsetbanks of parallel membrane modules.

The drawings of FIGS. 1–16 are not necessarily to scale.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention are directed toward the design andoperation of ion transport membrane systems that utilize multiplemembrane modules operating in series for use in either oxygen recoveryor oxidation processes. It has been found that when oxygen transportacross a membrane results in an exothermic reaction, for example in theproduction of synthesis gas from methane, the degree of reactantconversion across an individual membrane must be limited to prevent anexcessive temperature gradient across the membrane. It also has beenfound that when a membrane is transporting oxygen into a lower-pressurepermeate stream, the amount of oxygen extraction across an individualmembrane must be limited to prevent an excessive oxygen vacancy gradientin the membrane material between the leading edge and trailing edge ofthe membrane. Excessive temperature or oxygen vacancy gradients maycause excessive stresses in the membranes that could limit the membranelife quite drastically.

The present invention addresses these problems by orienting multiplemembrane modules or banks of modules in series so that the amount ofoxygen extracted across membranes in each module is sufficiently low toprevent an excessive oxygen vacancy gradient in the membrane material.The amount of oxygen extracted across each individual module may belimited by appropriate module sizing, and the total desired degree ofoxygen extraction may be achieved by operating a selected plurality ofmodules in series. When oxygen transport across a membrane results in anexothermic reaction, the degree of reactant conversion across individualmembranes in each module should be sufficiently low to prevent anexcessive temperature gradient across the membrane in the flowdirection. The degree of conversion across each individual module may belimited by appropriate module sizing, and the total desired conversionmay be achieved by operating a plurality of selected modules in series.

The gas flowing over the outside of the membranes in each membranemodule preferably is at a higher pressure than the gas on the inside ofthe membranes in the interior of the module as described below. In orderto minimize gas-phase mass transport resistance, the higher pressure gasshould be directed across the outer surface of the membranes at highvelocity and as uniformly as possible.

Because of the unique operating conditions of an ion transport membranesystem, the system design may include a pressure vessel, an optional gasflow containment device or duct disposed within the vessel andsurrounding the series membrane modules, and thermal insulation withinthe vessel to allow the vessel wall to operate at a lower temperaturethan the membrane modules. The proper physical positioning of each ofthese components as described below improves the prospects forfabrication, installation, and long-term operability of the system. Inaddition, other internal design features are disclosed that maycontribute to the long-term reliability of the overall ion transportmembrane system.

The following definitions apply to terms used in the description of theembodiments of the invention presented herein.

An ion transport membrane module is an assembly of a plurality ofmembrane structures which has a gas inflow region and a gas outflowregion disposed such that gas flows across the external surfaces of themembrane structures. Gas flowing from the inflow region to the outflowregion of a membrane module changes in composition as it passes acrossthe surfaces of the membrane structures in the module. Each membranestructure has an oxygen-containing gas feed side and a permeate sideseparated by an active membrane layer or region that allows oxygen ionsto permeate therethrough. Each membrane structure also has an interiorregion and an exterior region. In one embodiment, in which the membranemodule is operated as an oxygen separation device, the oxygen-containinggas feed side may be adjacent to the exterior region of the membranestructure and the permeate side may be adjacent to the interior regionof the membrane structure.

In an alternative embodiment, in which the membrane module is operatedas an oxidation reaction device, the oxygen-containing gas feed side maybe adjacent to the interior region of the membrane structure and thepermeate side may be adjacent to the exterior region of the membranestructure. In this alternative embodiment, a reactant feed gas flowsthrough the exterior region of the membrane structure and reacts withthe permeated oxygen. Thus in this embodiment the permeate side is alsothe reactant gas side of the membrane structure.

A membrane structure may have a tubular configuration in which anoxygen-containing gas flows in contact with one side of the tube (i.e.,in either the interior region or the exterior region of the tube) andoxygen ions permeate through active membrane material in or on the tubewalls to the other side of the tube. The oxygen-containing gas may flowinside or outside of the tube in a direction generally parallel to thetube axis, or conversely may flow over the outer side of the tube in adirection which is not parallel to the tube axis. A module comprisesmultiple tubes arranged in bayonet or shell-and-tube configurations withappropriate tube sheet assemblies to isolate the feed and permeate sidesof the multiple tubes.

Alternatively, the membrane structure may have a planar configuration inwhich a wafer having a center or interior region and an exterior regionis formed by two parallel planar members sealed about at least a portionof the peripheral edges thereof. Oxygen ions permeate through activemembrane material that may be placed on either or both surfaces of aplanar member. Gas can flow through the center or interior region of thewafer, and the wafer has one or more gas flow openings to allow gas toenter and/or exit the interior region of the wafer. Thus oxygen ions maypermeate from the exterior region into the interior region, orconversely may permeate from the interior region to the exterior region.

Components of a membrane module include an active membrane layer thattransports or permeates oxygen ions and may also transport electrons,structural components that support the active membrane layer, andstructural components to direct gas flow to and from the membranesurfaces. The active membrane layer typically comprises mixed metaloxide ceramic material and also may comprise one or more elementalmetals. The structural components of the membrane module may be made ofany appropriate material such as, for example, mixed metal oxide ceramicmaterials, and also may comprise one or more elemental metals. Any ofthe active membrane layer and structural components may be made of thesame material.

Single modules may be arranged in series, which means that a number ofmodules are disposed along a single axis. Typically, gas which haspassed across the surfaces of the membrane structures in a first moduleflows from the outflow region of that module, after which some or all ofthis gas enters the inflow region of a second module and thereafterflows across the surfaces of the membrane structures in the secondmodule. The axis of a series of single modules may be parallel or nearlyparallel to the overall flow direction or axis of the gas passing overthe modules in series.

Modules may be arranged in banks of two or more parallel modules whereina bank of parallel modules lies on an axis that is not parallel to, andmay be generally orthogonal to, the overall flow direction or axis ofthe gas passing over the modules. Multiple banks of modules may bearranged in series, which means by definition that banks of modules aredisposed such that at least a portion of gas which has passed across thesurfaces of the membrane structures in a first bank of modules flowsacross the surfaces of the membrane structures in a second bank ofmodules.

Any number of single modules or banks of modules may be arranged inseries. In one embodiment, the modules in a series of single modules orin a series of banks of modules may lie on a common axis or common axesin which the number of axes equals one or equals the number of modulesin each bank. In another embodiment described below, successive modulesor banks of modules in a series of modules or banks of modules may beoffset in an alternating fashion such that the modules lie on at leasttwo axes or on a number of axes greater than the number of modules in abank, respectively. Both of these embodiments are included in thedefinition of modules in series as used herein.

Preferably, the gas in contact with the outer surfaces in the exteriorregions of the membrane modules is at a higher pressure than the gaswithin the interior regions of the membrane modules.

A flow containment duct is defined as a conduit or closed channelsurrounding a plurality of series membrane modules which directs flowinggas over modules in series.

A manifold is an assembly of pipes or conduits which directs gas toenter and/or exit the interior regions of the membrane modules. Twomanifolds may be combined by installing a first or inner conduit withina second or outer conduit wherein the first conduit provides a firstmanifold and the annulus between the conduits provides a secondmanifold. The conduits may be concentric or coaxial, wherein these twoterms have the same meaning. Alternatively, the conduits may not beconcentric or coaxial but may have separate parallel or nonparallelaxes. This configuration of inner and outer conduits to provide acombined manifold function is defined herein as a nested manifold.

Flow communication means that components of membrane modules and vesselsystems are oriented relative to one another such that gas can flowreadily from one component to another component.

A wafer is a membrane structure having a center or interior region andan exterior region wherein the wafer is formed by two parallel planarmembers sealed about at least a portion of the peripheral edges thereof.Active membrane material may be placed on either or both surfaces of aplanar member. Gas can flow through the center or interior region of thewafer, i.e., all parts of the interior region are in flow communication,and the wafer has one or more gas flow openings to allow gas to enterand/or exit the interior region of the wafer. The interior region of thewafer may include porous and/or channeled material that allows gas flowthrough the interior region and mechanically supports the parallelplanar members. The active membrane material transports or permeatesoxygen ions but is impervious to the flow of any gas.

Oxygen is the generic term for forms of oxygen comprising the elementhaving an atomic number of 8. The generic term oxygen includes oxygenions as well as gaseous oxygen (O₂ or dioxygen). An oxygen-containinggas may include, but is not limited to, air or gas mixtures comprisingone or more components selected from the group consisting of oxygen,nitrogen, water, carbon monoxide, and carbon dioxide.

A reactant gas or reactant feed gas is a gas comprising at least onecomponent which reacts with oxygen to form an oxidation product. Areactant gas may contain one or more hydrocarbons, wherein a hydrocarbonis a compound comprising primarily or exclusively hydrogen and carbonatoms. A hydrocarbon also may contain other atoms, such as, for example,oxygen.

Synthesis gas is a gas mixture containing at least hydrogen and carbonoxides.

An ion transport membrane is an active layer of ceramic membranematerial comprising mixed metal oxides capable of transporting orpermeating oxygen ions at elevated temperatures. The ion transportmembrane also may transport electrons as well as oxygen ions, and thistype of ion transport membrane typically is described as a mixedconductor membrane. The ion transport membrane also may include one ormore elemental metals thereby forming a composite membrane.

An ion transport membrane system is a generic term for an array ofmultiple ion transport membrane modules used for oxygen recovery or foroxidation reactions. An ion transport membrane separation system is anion transport membrane system used for separating and recovering oxygenfrom an oxygen-containing gas. An ion transport membrane reactor systemis an ion transport membrane system used for oxidation reactions.

The series membrane modules in the embodiments of the present inventionmay be fabricated in either tubular or planar configurations asdescribed above. Planar configurations are preferred for manyapplications, and various configurations of planar membrane modules arepossible. Planar membrane module configurations are described, forexample, in copending U.S. patent application having Ser. No. 10/394,620filed on Mar. 21, 2003, which application is incorporated herein byreference.

The use of the indefinite articles “a” and “an” means one or more whenapplied to any feature of the present invention described in thespecification and claims. The use of “a” and “an” does not limit themeaning to a single feature unless such a limit is specifically stated.

An exemplary planar membrane module is illustrated in FIG. 1, which is aschematic front view of a membrane wafer stack or module for use inoxygen recovery or in oxidation processes according to embodiments ofthe present invention. The stack or module in this example comprises aplurality of planar wafers 1 separated by hollow spacers 3 and having anoptional cap 5. The wafers and spacers are placed and joined inalternating fashion as shown and form stack or module axis 7. The wafersmay be any shape in plan view, but square or rectangular shapes aregenerally preferred. The dimension of any side of a square orrectangular wafer may be between 2 and 45 cm. The number of wafers in astack may range up to 1000.

The exterior region of the stack or module is that region surroundingthe outer surfaces of the wafers and spacers. As described in detailbelow, wafers 1 have interior regions which are placed in flowcommunication with the interiors of spacers 3 wherein gas-tight sealsare formed between the wafers and spacers. Opening 9 in bottom hollowspacer 11 allows gas to enter and/or exit the interior region of thestack or module wherein the interior region of the module is formed bythe interior regions of the wafers and the openings in the hollowspacers. Thus opening 9 is in flow communication with the interiorregion of the module.

A side view of the module of FIG. 1 is shown in FIG. 2A, whichillustrates an exemplary configuration for use in oxidation processes.In this example, spacers 201 between wafers 200 each have two separatesets of openings 203 and 205. Openings 203 in spacers 201, andadditional openings in spacers disposed above and below spacers 201,form an internal manifold that is in flow communication with theinterior regions of the wafers by way of appropriately placed openings(not shown) through the layers of the wafers at the left ends of thewafers. These openings through the layers of the wafers also place theinternal openings 203 of spacers 201 and the internal openings inspacers above and below spacers 201 in flow communication with eachother. Likewise, openings 205 in spacers 201, and additional openings inspacers disposed above and below spacers 201, form an internal manifoldthat is in flow communication with the interior regions of the wafers byway of appropriately placed openings (not shown) through the layers ofthe wafers at the right ends of the wafers. These openings through thelayers of the wafers also place the internal openings 205 of spacers 201and the internal openings in spacers above and below spacers 201 in flowcommunication with each other.

In this example configuration, gas stream 207 flows upward through theinternal manifold formed by openings 203 and openings above them, andthen flows horizontally through the interior regions of the wafers. Gasfrom the interior regions of the wafers then flows downward through theinterior manifold formed by openings 205 and openings above them, andexits the module as gas stream 209. A second gas 211 at the gas inflowregion of the module flows through the exterior region of the module oneither side of spacers 201 and in contact with the outer surfaces ofwafers 200. Gas 213, after contacting the outer surfaces of wafers 200,flows through the gas outflow region of the module. The module mayoperate in a typical temperature range of 600 to 1100° C.

The module of FIG. 2A may be used as part of an oxidation reactor systemwherein representative gas 211 is a reactant gas and representative gas207 is an oxidant or oxygen-containing gas. The oxygen-containing gas207 flows through the internal manifold via openings 203 and through theinterior regions of the wafers, oxygen permeates the active membranematerial in the planar members of the wafers, and oxygen-depleted gas209 flows from the module via openings 205. Permeated oxygen reacts withreactant components in reactant gas or reactant feed gas 211 as the gasflows over the outer surfaces of the wafers and forms oxidationproducts. Exit gas 213 from the module contains the oxidation productsand unreacted components. In one example embodiment, reactant gas 211comprises methane or a methane-containing feed gas and exit gas 213 is amixture of unreacted methane, hydrogen, carbon oxides, and water,oxygen-containing gas 207 is air, and oxygen-depleted gas 209 isenriched in nitrogen and depleted in oxygen relative to gas 207.Typically, the pressure of gases 211 and 213 is higher than the pressureof the gas in the interior region of the module.

An alternative side view of the module of FIG. 1 is shown in FIG. 2B,which illustrates an exemplary configuration for use in processes forthe recovery of high purity oxygen from an oxygen-containing gas. Inthis example, spacers 215 between wafers 217 have openings 219 whereinopenings 219 and additional openings in spacers disposed below spacers215 form an internal manifold that is in flow communication with theinterior regions of the wafers. Opening 221 thus places the interiorregion of the module in flow communication with a product gas conduit(not shown). Oxygen-containing gas 223, for example air, at the gasinflow region of the module flows through the exterior region of themodule on either side of spacers 215 and in contact with the outersurfaces of wafers 217. After contacting the outer surfaces of wafers217, oxygen-depleted gas 225 flows through the gas outflow region of themodule. The module may operate in a typical temperature range of 600° C.to 1100° C.

As the oxygen-containing gas flows through the exterior region of themodule and the gas contacts the outer surfaces of the wafers, oxygenpermeates the active membrane material in the planar members of thewafers and high purity oxygen gas collects in the interior region of themodule. High purity oxygen product gas 227 flows from opening 221.Typically, the pressure of oxygen-containing gases 223 and 225 is higherthan the pressure of the high purity oxygen in the interior region ofthe module.

One possible exemplary configuration of the interior regions of thewafers in FIGS. 1, 2A, and 2B is illustrated in the sectional views ofFIGS. 3A and 3B. Referring to FIG. 3A, which represents section 2—2 ofFIG. 1, the wafer has outer support layers 301 and 303 of porous ceramicmaterial that allows gas flow through the pores. Dense active membranelayers of 305 and 307 are in contact with outer support layers 301 and303 and are supported by supporting ribs 321 and 329 which are part offlow channel layers 315 and 317. These ribs are in turn supported byslotted support layer 309 that has openings or slots 313 for gas flow.Open channels 319 and 325 are in flow communication via openings orslots 313. Optionally, support layers 301 and 303 may not be requiredwhen the module of FIG. 2B is used for recovering oxygen from anoxygen-containing gas.

The term “dense” refers to a ceramic material through which, whensintered or fired, a gas cannot flow. Gas cannot flow through denseceramic membranes made of mixed-conducting multi-component metal oxidematerial as long as the membranes are intact and have no cracks, holes,or imperfections which allow gas leaks. Oxygen ions can permeate denseceramic membranes made of mixed-conducting multi-component metal oxidematerial at elevated temperatures, typically greater than 600° C.

FIG. 3B, which represents section 4—4 of FIGS. 2A and 2B, illustrates awafer section rotated 90 degrees from the section of FIG. 3A. Thissection shows identical views of outer support layers 301 and 303 and ofdense active membrane material layers 305 and 307. This section alsoshows alternate views of slotted support layer 309 and flow channellayers 315 and 317. Open channels 331 are formed between alternatingsupporting ribs 333 and allow gas flow through the interior region ofthe wafer. The interior region of the wafer is therefore defined as thecombined open volume within flow channel layer 315, flow channel layer317, and slotted support layer 309.

The dense active membrane layers 305 and 307 preferably comprise a mixedmetal oxide ceramic material containing at least one mixed-conductingmulti-component metal oxide compound having the general formula(La_(x)Ca_(1-x))_(y)FeO_(3-δ) wherein 1.0>x>0.5, 1.1≧y≧1.0, and δ is anumber which renders the composition of matter charge neutral. Anyappropriate material can be used for porous support layers 301 and 303,and this material may be, for example, a ceramic material having thesame composition as that of active membrane layers 305 and 307.Preferably, porous support layers 301 and 303 are mixed-conductingmulti-component metal oxide material. Any appropriate material can beused for the structural members of slotted support layer 309 and flowchannel layers 315 and 317, and this material may be, for example, aceramic material having the same composition as that of active membranelayers 305 and 307. The material of channeled support layer preferablyis a dense ceramic material. In one embodiment, active membrane layers305 and 307, porous support layers 301 and 303, slotted support layer309, and flow channel layers 315 and 317 all may be fabricated ofmaterial having the same composition.

Dense active membrane layers 305 and 307 optionally may include one ormore oxygen reduction catalysts on the oxidant side. The catalyst orcatalysts may comprise metals selected from or compounds containingmetals selected from the group consisting of platinum, palladium,ruthenium, gold, silver, bismuth, barium, vanadium, molybdenum, cerium,praseodymium, cobalt, rhodium and manganese.

Porous support layers 301 and 303 optionally may include one or morecatalysts to promote hydrocarbon oxidation, reforming, and/or otherreactions that occur in the porous layer. The catalyst or catalysts maybe disposed on either or both surfaces of porous support layers 301 and303, or alternatively may be dispersed throughout the layer. The one ormore catalysts may comprise metals selected from or compounds containingmetals selected from the group consisting of platinum, palladium,rhodium, ruthenium, iridium, gold, nickel, cobalt, copper, potassium andmixtures thereof. If desired for structural and/or process reasons, anadditional porous layer may be disposed between active membrane layers305 and 307 and the adjacent flow channel layers 315 and 317respectively.

Another possible configuration of the interior regions of the wafers forthe oxygen recovery application in FIGS. 1, 2A, and 2B are illustratedin the sectional views of FIGS. 3C and 3D. Referring to FIG. 3C, whichrepresents section 2—2 of FIG. 1, the wafer has outer dense layers 351and 353. Porous ceramic layers of 355 and 357 are in contact with outerdense layers 351 and 353. Porous ceramic layer 355 is supported bysupporting ribs 371, which are part of flow channel layer 365. Porousceramic layer 355 is in contact with flow channels 366, which are partof flow channel layer 365. Porous ceramic layer 357 is in contact withflow channels 368, which are part of flow channel layer 367.

Ribs 371 are supported in turn by flow channel layer 358 that hasopenings or slots 363 for gas flow. Flow channel layer 367 is supportedby ribs 373 of flow channel layer 359, and bridges 379 form the ends offlow channels 368. Bridges 372 form the ends of the flow channels 363and flow channels 368 are in flow communication with flow channels 374of flow channel layer 359. Open channels 374 and 363 are in flowcommunication.

FIG. 3D, which represents section 4—4 of FIGS. 2A and 2B, illustrates asection of the wafers rotated 90 degrees from the section of FIG. 3C.This section shows identical views of outer dense layers 351 and 353 andof porous ceramic layers 355 and 357. Porous ceramic layer 355 issupported by flow channel layer 365. Porous ceramic layer 355 is incontact with flow channels 366, which are part of flow channel layer365. Porous ceramic layer 357 is supported by ribs 378 of flow channellayer 367. Porous layer 357 is in flow communication with flow channels368, which are part of flow channel layer 367.

Ribs 378 are supported in turn by flow channel layer 359 that hasopenings or slots 374 for gas flow. Flow channel layer 365 is supportedby ribs 375 of flow channel layer 358. Bridges 371 form the ends of flowchannels 366. Bridges 376 form the ends of the flow channels 374 andflow channels 366 are in flow communication with flow channels 363 offlow channel layer 358. Open channels 374 and 363 are in flowcommunication.

The interior region of the wafer therefore is defined as the combinedopen volume within flow channel layer 365, flow channel layer 367, flowchannel layer 358 and flow channel layer 359. The flow channels inlayers 365 and 358 may be orthogonal to each other, as may be the flowchannels in layers 367 and 359. Alternatively, flow channels 358 and 359may be replaced by a single flow channel layer that comprises flowchannels that radiate from the center of the wafer and are in flowcommunication with a central port in the center of the wafer.

Exemplary compositions for the dense active membrane are described inU.S. Pat. No. 6,056,807, which is incorporated herein by reference.Dense active membrane layers 351 and 353 preferably comprise a mixedmetal oxide ceramic material containing at least one mixed-conductingmulti-component metal oxide compound having the general formula(La_(x)Sr_(1-x))Co_(y)O_(3-δ) wherein 1.0<x<0.4, 1.02≧y>1.0, and δ is anumber which renders the composition of matter charge neutral. Anyappropriate ceramic material can be used for porous support layers 355and 357, and may be, for example, material of the same composition asthat of active membrane layers 351 and 353. Preferably, porous supportlayers 355 and 357 are mixed-conducting multi-component metal oxidematerial. Any appropriate material can be used for the structuralmembers of flow channel layers 365, 367, 358 and 359, and this materialmay be, for example, a ceramic material having the same composition asthat of active membrane layers 351 and 353. The material of channeledflow layers preferably is a dense ceramic material. In one embodiment,active membrane layers 351 and 353, porous support layer 355 and 357,and channeled flow layers 358, 359, 365 and 367 all may be fabricated ofmaterial having the same composition.

Optionally, a porous layer may be applied on the outside surface ofdense layers 351 and 353. Other exemplary configurations for theinterior regions of the wafers for the oxygen generation application aregiven in U.S. Pat. No. 5,681,373, which is incorporated herein byreference.

Embodiments of the present invention utilize multiple membrane modulesarranged in series as defined above. The series modules in turn may beinstalled in one or more vessels with appropriate gas flow containmentducts, conduits, and/or manifolds to direct gas streams to and from themodules. One of these embodiments is illustrated in FIG. 4A, which is aschematic side view of the interior of an exemplary membrane separatorvessel for use in recovering high purity oxygen from anoxygen-containing gas. Membrane modules 401, 403, 405, 407, and 409 areinstalled in series in optional flow containment duct 411 withinpressure vessel 413. These membrane modules may be, for example, similarto the module described above with reference to FIGS. 1 and 2B. Optionalflow containment duct 411 has inlet 415 to direct inlet gas stream 417through the duct to contact the outer surfaces of the wafers in modules401 to 409. The inlet gas stream is a pressurized oxygen-containingoxidant gas, for example air, that has been heated by any appropriatemethod (not shown) to a temperature of 600° C. to 1100° C. The pressureof the gas within duct 411 may be in the range of 0.2 to 8 MPa. The flowcontainment duct preferably comprises an oxidation-resistant metal alloycontaining iron and one or more elements selected from the groupconsisting of nickel and chromium. Commercially-available alloys thatmay be used for flow containment ducts include Haynes® 230, Incolloy800H, Haynes® 214, and Inconel® 693 alloys.

The gas pressure in the interior of flow containment duct 411 preferablyis greater than the gas pressure in the interior of pressure vessel 413between the inner wall of the vessel and the outer wall of flowcontainment duct 411. The pressure differential between the interior andthe exterior of duct 411 at any point between the inlet and outlet ofpressure vessel 413 preferably is maintained at a value equal to orgreater than zero, wherein the pressure in the interior of the duct isequal to or greater than the pressure in the pressure vessel exterior tothe duct. This may be accomplished, for example, by purging the spaceoutside the duct with a gas at lower pressure than the process gasinside the duct; allowing flow communication between the space outsidethe duct and the process gas in the duct at process gas outlet 421;introducing a purge gas into the space outside the duct, or withdrawingthe purge gas through a purge gas outlet while using pressurecontrollers on a purge gas outlet to maintain a lower pressure in thespace outside the duct than inside the duct.

As the oxygen-containing gas passes in series over the surfaces of thewafers in membrane modules 401 to 409, oxygen permeates the dense activemembrane layers and collects in the interior regions of the modules.Oxygen-depleted gas stream 419 exits the duct and pressure vessel viaoutlet 421. High purity oxygen permeate product from the interiorregions of the modules flows via primary manifolds 423, 425, 427, 429,and 431, secondary manifolds 433, 435, 437, 439, and 441, and mainmanifold 445, and exits the system as high purity gas product stream447. At least two of membrane modules 401 to 409 define a module axiswhich may be parallel to or coincident with the axis of pressure vessel413 or with the axis of flow containment duct 411.

While the exemplary membrane separator vessel described above has asingle inlet for feed gas to the membrane modules, a single flowcontainment duct, and a single outlet from the membrane modules, otherembodiments are possible in which multiple inlets, multiple flowcontainment ducts, and/or multiple outlets may be used. For example, apressure vessel may have two (or more) flow containment ducts, eachhaving one or more inlets and one or more outlets. Generically, when aseparator vessel is described as having an inlet and an outlet, thismeans that it has one or more inlets and one or more outlets.Generically, when a separator vessel is described as having a flowcontainment duct, this means that it has one or more flow containmentducts.

Another view of the exemplary membrane separator vessel of FIG. 4A isgiven by section 6—6 as shown in FIG. 4B. In this embodiment, a bank ofthree membrane modules 401 a, 401 b, and 401 c is installed in parallelin duct 411 and has three primary manifolds 423 a, 423 b, and 423 c thatare connected to secondary manifold 433. Secondary manifold 433 isconnected in turn to main manifold 445. Alternatively, one membranemodule, two parallel membrane modules, or more than three parallelmembrane modules may be used in each bank.

While secondary manifolds 433, 435, 437, 439, and 441, and main manifold445 are located in the interior of pressure vessel 413 in theembodiments of FIGS. 4A and 4B, these manifolds may be located outsideof the pressure vessel in an alternative embodiment. Primary manifolds423, 425, 427, 429, and 431 would pass through the wall of pressurevessel 413 in this alternative embodiment.

In an alternative embodiment, planar membrane modules 401 through 409may be replaced by tubular membrane modules placed in seriesrelationship relative to the longitudinal flow of gas through optionalduct 411. These modules may utilize multiple single tubes or may utilizebayonet-type tubes, and the modules may be oriented such that gas flowsacross the tubes in crossflow or contacts the tubes in parallel flow. Inthis alternative embodiment, all manifolds are located inside thepressure vessel as shown in FIGS. 4A and 4B.

Another embodiment of the invention is illustrated in FIG. 5, which is aschematic side view of the interior of an exemplary membrane reactorvessel for use in oxidation processes. Membrane modules 501, 503, 505,507, and 509 are installed in series in flow containment duct 511 withinpressure vessel 513. These membrane modules may be, for example, similarto the module described above with reference to FIGS. 1 and 2A. Optionalflow containment duct 511 has inlet 515 to direct inlet gas stream 517through the duct to contact the outer surfaces of the wafers in modules501 to 509. The inlet gas stream is a reactant feed gas containing oneor more components which react with oxygen at elevated temperatureswherein the inlet reactant feed gas is heated by any appropriate method(not shown) to a temperature of 600° C. to 1100° C. The pressure of thegas within duct 511 may be in the range of 0.2 to 8 MPa. An example of areactant feed gas is a mixture of steam and natural gas wherein thenatural gas comprises mostly methane with smaller amounts of lighthydrocarbons. The mixture may be prereformed at a temperature belowabout 800° C. to yield a reactant feed gas containing steam, methane,and carbon oxides. Other oxidizable reactant feed gases may include, forexample, various mixtures of hydrogen, carbon monoxide, steam, methanol,ethanol, and light hydrocarbons.

The gas pressure in the interior of flow containment duct 511 preferablyis greater than the gas pressure in the interior of pressure vessel 513between the inner wall of the vessel and the outer wall of flowcontainment duct 511. The pressure differential between the interior andthe exterior of duct 511 at any point between the inlet and outlet ofpressure vessel 513 preferably is maintained at a value equal to orgreater than zero, wherein the pressure in the interior of the duct isequal to or greater than the pressure in the pressure vessel exterior tothe duct. This may be accomplished, for example, by purging the spaceoutside the duct with a gas at lower pressure than the process gasinside the duct; allowing flow communication between the space outsidethe duct and the process gas in the duct at the process gas outlet, 559;introducing a purge gas into the space outside the duct, and withdrawingthe purge gas through a purge gas outlet while using pressurecontrollers on a purge gas outlet to maintain a lower pressure in thespace outside the duct than inside the duct.

The interior regions of membrane modules 501 to 509 are in flowcommunication with two manifold systems, one to introduce anoxygen-containing oxidant gas into the modules and the other to withdrawoxygen-depleted oxidant gas from the modules. The first of thesemanifold systems comprises main inlet manifold 519, primary inletmanifolds 521, 523, 525, 527, and 529, and secondary inlet manifolds531, 533, 535, 537, and 539. The second of these manifold systemscomprises main outlet manifold 541 and primary outlet manifolds 543,545, 547, 549, and 551.

In an alternative configuration (not shown) to the configuration of FIG.5, secondary inlet manifolds 531, 533, 535, 537, and 539 may be combinedwith primary outlet manifolds 543, 545, 547, 549, and 551, respectively,when located within flow containment duct 511. Two manifolds may becombined by installing a first or inner conduit within a second or outerconduit wherein the first conduit provides a first manifold and theannulus between the conduits provides a second manifold. The conduitsmay be concentric or coaxial; alternatively, the conduits may not beconcentric or coaxial and may have separate parallel or nonparallelaxes. This configuration of inner and outer conduits to provide acombined manifold function is defined herein as a nested manifold.

In this alternative configuration, gas 553 would flow through thecentral conduit and gas 555 would flow through the annulus of each setof these nested manifolds. The nested manifolds would transition toseparate manifolds exterior to flow containment duct 511, i.e., wouldtransition to secondary inlet manifolds 531, 533, 535, and 539 andprimary outlet manifolds 543, 545, 547, 549, and 551 as shown in FIG. 5.Optionally, primary outlet manifolds 543, 545, 547, 549, and 551 may benested within secondary inlet manifolds 531, 533, 535, 537, and 539,respectively, within flow containment duct 511. In this option, gas 555would flow through the central conduit and gas 553 would flow throughthe annulus of each set of these nested manifolds. In generic terms,therefore, the secondary inlet manifolds and the primary outletmanifolds may be nested when located within flow containment duct 511,and either a secondary inlet manifold or a primary outlet manifold maybe provided by the annulus

Heated, pressurized oxygen-containing oxidant gas 553, for example, airthat has been heated by any appropriate method (not shown) to atemperature of 600 to 1100° C., enters main inlet manifold 519 and flowsvia primary inlet manifolds 521, 523, 525, 527, and 529 and secondaryinlet manifolds 531, 533, 535, 537, and 539 to the inlets of membranemodules 501, 503, 505, 507, and 509. Oxygen from the oxidant gas in theinterior regions of the membrane modules permeates the dense activemembrane layers in the wafers of modules 501 to 509 and the permeatedoxygen reacts with the reactive components in the exterior regions ofthe membrane modules. Oxygen-depleted oxidant gas exits the oulets ofthe interior regions of the membrane modules via primary outletmanifolds 543, 545, 547, 549, and 551 and main outlet manifold 541, andthe final oxygen-depleted oxidant gas is withdrawn as gas stream 555.Outlet gas stream 557, which contains reaction products and unreactedfeed components, is withdrawn from the reactor system via outlet 559.

While the exemplary reactor vessel described above has a single inletfor reactant feed gas to the membrane modules, a single flow containmentduct, and a single outlet from the membrane modules, other embodimentsare possible in which multiple inlets, multiple flow containment ducts,and/or multiple outlets may be used. For example, a pressure vessel mayhave two or more flow containment ducts, each having one or more inletsand one or more outlets. Generically, when a reactor vessel is describedas having an inlet and an outlet, this means that it has one or moreinlets and one or more outlets. Generically, when a reactor vessel isdescribed as having a flow containment duct, this means that it has oneor more flow containment ducts.

Another view of the exemplary membrane reactor vessel of FIG. 5 is givenin section 8—8 as shown in FIG. 6. In this embodiment, a bank of threemembrane modules 503 a, 503 b, and 503 c are installed in parallel induct 511. Oxidant gas flows through main inlet manifold 519, primaryinlet manifold 523, and secondary inlet manifolds 533 a, 533 b, and 533c to the inlets of membrane modules 503 a, 503 b, and 503 c.Oxygen-depleted oxidant gas exits membrane modules 503 a, 503 b, and 503c via primary outlet manifolds 545 a, 545 b, and 545 c (located behindsecondary inlet manifolds 533 a, 533 b, and 533 c), secondary outletmanifold 561, and main outlet manifolds 541 a and 541 b. While threeparallel membrane modules are shown in the embodiment of FIG. 6, onemembrane module, two parallel membrane modules, or more than threeparallel membrane modules may be used as desired.

A guard bed (not shown) may be installed in inlet 415 of pressure vessel413 and/or in inlet 515 to pressure vessel 513 to remove tracecontaminants from inlet stream 417 and/or 517. Alternatively, the guardbed may be installed in the interior of the pressure vessel between theinlet and the first membrane module. The contaminants may include, forexample, sulfur-, chromium- and/or silicon-containing gaseous species.The guard bed may contain one or more materials selected from the groupconsisting of magnesium oxide, calcium oxide, copper oxide, calciumcarbonate, sodium carbonate, strontium carbonate, strontium oxide, zincoxide, and alkaline-earth-containing perovskites. These materials reactwith and remove the contaminants from the inlet stream of reactant gasor oxygen-containing gas.

Additional pressure vessels may be installed in series with pressurevessel 413 such that the outlet gas from one vessel feeds the othervessel. Additional pressure vessels may be placed in parallel wherein aplurality of pressure vessels operate in parallel and in series.Likewise, additional pressure vessels may be installed in series withpressure vessel 513 such that the outlet gas from one vessel feeds theother vessel. Additional pressure vessels may be placed in parallelwherein a plurality of pressure vessels operate in parallel and inseries. Guard beds may be placed between any series pressure vessels asdesired.

In the embodiments described above, it is desirable to use internalinsulation to maintain the walls of pressure vessel 413 and 513 attemperatures lower than the temperatures of the respective membranemodules 401 to 409 and 501 to 509. This may be accomplished by variousinsulation alternatives in FIGS. 7 through 13, which illustrateinsulation configurations for the embodiment of FIGS. 4A and 4B used forthe recovery of oxygen from an oxygen-containing gas. Similar insulationconfigurations (not shown) may be used for the oxidation reactorembodiment of FIGS. 5 and 6.

The first of these alternatives is shown in FIG. 7 wherein insulation701 is disposed within and may be in contact with the interior walls ofpressure vessel 703. In this embodiment, a flow containment duct is notused; instead, cavity 705 is formed by the insulation itself and thiscavity serves to direct gas flow over the exterior regions of themembrane modules. The insulation may be in contact with primarymanifolds 423 a, 423 b, and 423 c, secondary manifold 433, and mainmanifold 445.

A second insulation configuration is shown in FIG. 8 wherein insulation801 is disposed adjacent to and may be in contact with the inner wall ofpressure vessel 413. In this embodiment, flow containment duct 411 isused and preferably is not in contact with insulation 801. Theinsulation preferably is not in contact with primary manifolds 423 a,423 b, and 423 c, secondary manifold 433, and main manifold 445.

A third insulation configuration is shown in FIG. 9 wherein insulation901 completely fills the interior region of the pressure vessel betweenthe inner walls of the vessel and the exterior surfaces of flowcontainment duct 411, primary manifolds 423 a, 423 b, and 423 c,secondary manifold 433, and main manifold 445. The insulation may be incontact with the inner vessel walls and the exterior surfaces of flowcontainment duct 411, primary manifolds 423 a, 423 b, and 423 c,secondary manifold 433, and main manifold 445.

Another alternative insulation configuration is shown in FIG. 10 whereininsulation 1001 forms a cavity 1003 around the membrane modules and thiscavity serves to direct gas flow over the exterior regions of themodules. Insulation 1001 may be in contact with primary manifolds 423 a,423 b, and 423 c, and typically is not in contact with the inner wallsof pressure vessel 413.

FIG. 11 shows another alternative insulation configuration in whichinsulation 1101 surrounds flow containment duct 411, which in turnsurrounds the membrane modules as described above. Insulation 1101 maybe in contact with primary manifolds 423 a, 423 b, and 423 c, andtypically is not in contact with the inner walls of pressure vessel 413and the outer surface of flow containment duct 411.

Another insulation configuration is shown in FIG. 12 wherein insulation1201 surrounds flow containment duct 411, which in turn surrounds themembrane modules as described above. Insulation 1201 may be in contactwith primary manifolds 423 a, 423 b, and 423 c, typically is in contactwith the outer surface of flow containment duct 411, and typically isnot in contact with the inner walls of pressure vessel 413.

A final insulation configuration is shown in FIG. 13 wherein insulation1303 is placed within and typically in contact with the inner walls offlow containment duct 411, wherein the insulation forms a cavity 1305around the membrane modules and this cavity serves to direct gas flowover the exterior regions of the modules. Insulation 1303 may be incontact with primary manifolds 423 a, 423 b, and 423 c.

In any of the embodiments described above of FIGS. 7–13, ametal-to-ceramic seal typically is used in primary manifolds 423 a, 423b, and 423 c to transition from metal manifolds to the ceramic modules.Likewise, in the oxidation reactor embodiment of FIG. 6 andcorresponding insulation embodiments similar to those of FIGS. 7–13, ametal-to-ceramic seal typically is used in primary manifolds 533 a, 533b, and 533 c to transition from metal manifolds to the ceramic modules.In the embodiments of FIGS. 10–13 (and similar embodiments for theoxidation reactor), these seals preferably are located within insulation1001, 1101, 1201, and 1303 (in contact with manifolds 423 a, 423 b, and423 c but not with manifold 433) to obtain desired seal operatingtemperatures.

In any of the embodiments of FIGS. 7–13, additional insulation (notshown) may be placed around the external surface of the pressure vessel,for example to protect operating personnel from a potentially hot vesselsurface. This additional insulation also may serve to ensure that thevessel interior is above the dew point of any gas within the vessel. Inany of the embodiments of FIGS. 10–13, additional insulation (not shown)may be placed adjacent to the inner surface of the pressure vessel. Inany of the embodiments of FIGS. 4A, 4B, and 5–13, any of the manifoldsmay be insulated internally and/or externally (not shown). Thisinsulation would serve to improve the thermal expansion uniformity offlow containment duct 411 and the manifolds.

The insulation used in the embodiments of FIGS. 7–13 may containalumina, alumino-silicate, silica, calcium silicate, or otherconventional insulation materials suitable for use at elevatedtemperatures. The insulation may comprise, for example, one or morematerials selected from the group consisting of fibrous alumina, fibrousalumino-silicate, porous alumina, and porous alumino-silicate. In theembodiments of FIGS. 7, 10, and 13, wherein the insulation itself formsa cavity around the membrane modules, the interior walls of the cavitymay be coated or covered with a material which prevents volatilecomponents from the insulation from contacting the membrane modules. Forexample, the cavity may be lined with a foil made of a metal such asHaynes 214 to prevent Si-containing vapor species, which may begenerated from insulation materials, and/or Cr-containing vapor species,which may be generated from metal piping materials, from contacting themembrane modules.

The insulation may include one or more additional materials selectedfrom the group consisting of magnesium oxide, calcium oxide, copperoxide, calcium carbonate, strontium carbonate, sodium carbonate, zincoxide, strontium oxide, and alkaline-earth-containing perovskiteswherein these materials may be applied to the surface of the insulationand/or dispersed throughout the insulation. These additional materialsmay be used in place of or in addition to the guard bed or bedsdescribed above. These materials react with and remove contaminants thatmay be present in the inlet stream of reactant gas; these contaminantsmay include, for example, sulfur-, chromium-, silicon-, oroxygen-containing containing gaseous species.

An alternative embodiment for placing groups of wafers in a series flowconfiguration is shown in FIG. 14. In this embodiment, a tall stack isformed of wafers and spacers as described above and the stack isinstalled in pressure vessel 1401. Inlet line 1403 and outlet line 1405are connected to gas manifold shroud assembly 1407 which directs theflow of inlet gas 1408 to flow in alternating directions across groupsof wafers and through outlet line 1405 as outlet stream 1409. In thisembodiment, the stack is divided by the shroud assembly into first waferzone 1411, second wafer zone 1413, and third wafer zone 1415. Inlet gas1408 thus flows in series across wafer zones 1411, 1413, and 1415 andexits via outlet line 1405. While three wafer zones are shown here forillustration purposes, any number of wafer zones can be used asrequired.

The embodiment of FIG. 14 may be used as an oxygen recovery device or asan oxidation reactor device. When used as an oxygen recovery device, thestack is formed of wafers and spacers as earlier described withreference to FIGS. 1 and 2B. In an oxygen recovery process, inlet gas1408 is a heated, pressurized oxygen-containing gas (for example, air),outlet stream 1409 is an oxygen-depleted oxygen-containing gas, andstream 1417 flowing through outlet line 1419 is a high purity oxygenproduct stream typically at a lower pressure than the pressurizedoxygen-containing gas. When used as an oxidation reactor system, thestack is formed of wafers and spacers as earlier described withreference to FIGS. 1 and 2A. In an oxidation process, inlet gas 1408 isa heated, pressurized reactant gas and outlet gas 1409 is a mixture ofoxidation reaction products and unreacted reactant gas components.Stream 1417 is an oxygen-depleted oxygen-containing gas stream typicallyat a lower pressure than the pressurized reactant gas. Freshoxygen-containing oxidant gas (for example, air) flows into the stackthrough an internal stack manifold as described with reference to FIG.2A; the inlet to this manifold is not seen in FIG. 14 because it liesbehind outlet line 1419.

The embodiment of FIG. 14 can be operated with multiple pressure vesselsin series and/or in parallel as desired. Multiple modules may beinstalled in a single pressure vessel if desired.

The series membrane modules may be arranged in banks of parallel modulesas earlier described with reference to FIGS. 4A, 4B, 5, and 6. This isillustrated in FIG. 15, which is a sectional plan view (not to scale) offlow containment duct 511 and the membrane modules within the duct. Inthis exemplary embodiment, five banks of three parallel modules arearranged such that each individual set of series modules lies on acommon module axis, i.e., modules 501 a, 503 a, 505 a, 507 a, and 509 alie on the same axis, modules 501 b, 503 b, 505 b, 507 b, and 509 b lieon the same axis, and modules 501 c, 503 c, 505 c, 507 c, and 509 c lieon the same axis. Thus in this example there are three axes, equal tothe number of modules in each bank. Each bank comprises a plurality ofmodules in parallel; for example, modules 501 a, 501 b, and 501 cconstitute one bank of modules in parallel. A plurality of modules alsomay be arranged in series; for example, modules 501 c, 503 c, 505 c, 507c, and 509 c constitute modules in series. The definition of seriesmodules also can include banks of modules; for example, the bank ofmodules 501 a, 501 b, and 501 c is in series with the bank of modules503 a, 503 b, and 503 c. The module configuration in FIG. 15 thusincludes modules in series and modules in parallel.

As a practical matter, it may be desirable to promote substantial radialmixing (i.e., gas flow in directions deviating from the axis of a seriesof modules) of gas between successive banks of modules to minimize thedeleterious effect of gas bypassing around the membrane modules. Themodule configuration in FIG. 15 thus may be best described as includingmodules in parallel and banks of parallel modules operating in series.As in the design of many gas flow distribution systems, the degree ofradial mixing can be maximized by proper selection of the axial andradial spacing between internal elements (i.e. membrane modules) and/orthe use of flow baffles to promote gas mixing.

Inlet gas stream 1501 in inlet 1503 flows in series over each bank ofradially-oriented (i.e., parallel) modules. With proper selection of theaxial and radial spacing between modules, a small amount of gas maybypass modules 501 a, 501 b, and 501 c, but eventually will contactdownstream modules as it mixes or diffuses in a radial direction. Exitgas stream 1505 flows through outlet 1507. The gas flow over eachsuccessive bank of modules defines the series arrangement of thisembodiment wherein all or nearly all of the gas from one bank ofparallel modules contacts the next bank of parallel modules in theseries of modules. Any desired number of modules may be used in parallelradially and any desired number of banks of parallel modules may be usedin series axially.

In an alternative embodiment of the invention related to FIGS. 4A and 4Bor to FIGS. 5 and 6, banks of parallel membrane modules may be orientedin a staggered or offset series arrangement such that a first bank ofthree modules is followed in series by an offset second bank of threemodules which in turn is followed in series by an offset third bank ofthree modules, and so forth. This is illustrated in FIG. 16 wherein afirst bank of three modules 502 a, 502 b, and 502 c is followed inseries by a second bank of three modules 504 a, 504 b, and 504 c offsetin a direction perpendicular to the axis of flow containment duct 511. Athird bank of three modules 506 a, 506 b, and 506 c is offset withrespect to the second bank but the modules are coaxial with the modulesin the first bank. This offset relationship may continue in similarfashion through the fourth bank of modules 508 a, 508 b, and 508 c andthe fifth bank of modules 510 a, 510 b, and 510 c. Each bank maycomprise a plurality of modules in parallel; for example, modules 502 a,502 b, and 502 c constitute one bank of modules in parallel. A pluralityof modules also may be arranged in series; for example, modules 502 c,504 c, 506 c, 508 c, and 510 c may constitute modules in series. Thedefinition of series modules also can include banks of modules; forexample, the bank of modules 502 a, 502 b, and 502 c is in series withthe bank of modules 504 a, 504 b, and 504 c. The module configuration inFIG. 16 thus includes modules in series and modules in parallel.

The modules in FIG. 16 lie on six axes, i.e., modules 502 c, 506 c, and510 c lie on one axis, modules 504 c and 508 c lie on another axis, andso forth. These axes may be parallel to the overall flow direction ofgas over the modules. In this embodiment, the number of axes is greaterthan the number of modules in each bank of modules.

In the embodiment of FIG. 16, inlet gas stream 1601 enters through inlet1603 and flows over modules 502 a, 502 b, and 502 c in the first bank. Aportion of this gas may bypass module 502 a but, in the absence ofsignificant radial mixing, will at least contact offset module 504 a.Gas that flows between modules 502 a, 502 b, and 502 c, will at leastcontact the next series of offset modules 504 b and 504 c. Portions ofthe gas that flows from module 502 a in the first bank will contact atleast two modules (504 a and 504 b) in the second bank. In this way,such an offset arrangement prevents gas from bypassing straight througha gap between rows of modules on a common axis. Instead, gas bypassingany module in a bank of modules will impinge directly on a module in thenext bank of modules. In the absence of significant radial mixing, atleast a portion of the gas from one or more of the modules in a bankwill contact one or more of the modules in the next bank, and thisdefines the series arrangement of modules in this embodiment.

The definition of modules arranged in series according to the presentinvention thus includes both embodiments described above with referenceto FIGS. 15 and 16. In these embodiments, the axes of banks of modulesand the axes of series modules may be generally orthogonal, and the axesof series modules may be generally parallel to the overall direction ofgas flow through the vessel. Alternative embodiments are possiblewherein the axes of banks of modules are not generally orthogonal to theaxes of the series modules and/or wherein the axes of series modules arenot generally parallel to the overall direction of gas flow through thevessel. In these alternative embodiments, the banks of modules lie atacute angles to the overall direction of gas flow through the vessel.These alternative embodiments are included in the definition of modulesarranged in series according to the present invention.

The series reactor system described above may be used in oxidationservice to produce synthesis gas from a hydrocarbon-containing feed gassuch as natural gas. In this application, reforming catalyst may bedisposed between any series modules, any parallel modules, any seriesand parallel modules, and/or following the final modules in a vessel.The reforming catalyst promotes the endothermic reactions of waterand/or carbon dioxide with hydrocarbons, especially methane, to generatehydrogen and carbon monoxide. The catalyst may be used to complement orbalance the exothermic oxidation reactions that occur between permeatedoxygen and reactants adjacent to the surfaces of the active membranematerial in the modules. By appropriate use of reforming catalyst atstrategic locations between the modules in a multiple-module seriesreactor system, the temperature profiles across the reactor and theproduct gas composition may be controlled to achieve optimum reactoroperation.

An embodiment of the present invention is illustrated by the exemplaryplacement of appropriate catalyst between the modules of amultiple-module series oxidation reactor system. For example, referringto FIG. 15, catalyst 501 d, 501 e, and 501 f may be placed in seriesfashion in the space between any modules in the first bank of modules501 a, 501 b, and 501 c and the second bank of modules 503 a, 503 b, and503 c. Alternatively, catalyst 501 d, 501 e, and 501 f may extendcontinuously between the inner walls of flow containment duct 511.Likewise, catalyst may be placed between any or all of the second andthird banks of modules, the third and fourth bank of modules, the fourthand fifth banks of modules, or following the fifth bank (not shown).Similarly, catalyst may be placed in series fashion between any or allof the offset banks of modules in the embodiment of FIG. 16. Forexample, referring to FIG. 16, catalyst 502 d, 502 e, and 502 f may beplaced in series fashion in the space between the first and second banksof modules. Alternatively, catalyst 502 d, 502 e, and 502 f may extendcontinuously between the inner walls of flow containment duct 511. Ingeneral, catalyst may be placed in series fashion between or downstreamof any or all of the series banks of modules in FIGS. 15 and 16.

Additionally or alternatively, catalyst may be placed between themodules in a bank of parallel modules to promote reforming reactions inthe gas passing between the modules. For example, in FIG. 15 catalyst505 d and 505 e may be placed between modules 505 a and 505 b andbetween 505 b and 505 c. Alternatively, catalyst 505 d, and 505 e mayextend continuously in the axial direction between the first throughfifth banks of modules. For example, in FIG. 16 catalyst 506 d and 506 emay be placed between modules 406 a and 506 b and between 506 b and 506c. In general, catalyst may be placed in parallel fashion between any orall of the parallel modules in FIGS. 15 and 16.

In the broadest application of this concept, therefore, catalyst may beplaced in the space between any two adjacent modules in the embodimentsof FIGS. 15 and 16, or in any other embodiments with both of series andparallel module placement. In addition, when pressure vessel 513 isoperated in series with another similar pressure vessel, catalyst may beplaced between the vessels such that the effluent gas from one pressurevessel passes through the catalyst before passing into the secondpressure vessel.

The catalyst may be varied in type and/or amount depending on the axialor radial location among the modules in the pressure vessel. In onealternative, for example, the catalyst activity may be varied in theaxial direction for optimal control of the module temperatures throughthe reactor. For example, catalyst sections near the inlet of thereactor may comprise catalyst which is active at lower temperature (i.e.a high Ni loading), whereas in higher temperature regions of the reactorthe optimal catalyst composition may involve lesser activity and greaterthermal stability (i.e. a low Ni loading). In this way, optimal catalystactivity can be achieved at every axial location in the reactor, whilemaintaining thermal stability of the catalyst. Other catalystarrangements are possible and fall within the scope of embodiments ofthe claimed invention.

The catalyst for use in this embodiment may include one or more metalsor compounds containing metals selected from the group consisting ofnickel, cobalt, platinum, gold, palladium, rhodium, ruthenium, and iron.The catalyst may be supported on alumina or other oxide supports and mayinclude additions such as lanthanum or potassium. The catalyst may beplaced between modules by any known means including, for example, usingmonoliths or using granular catalysts in appropriate catalyst holdersthat fit in the spaces between the modules.

1. An ion transport membrane system comprising (a) a pressure vesselhaving an interior, an exterior, an inlet, and an outlet; (b) aplurality of planar ion transport membrane modules disposed in theinterior of the pressure vessel and arranged in series, each membranemodule comprising mixed metal oxide ceramic material and having aninterior region and an exterior region, wherein any inlet and any outletof the pressure vessel are in flow communication with exterior regionsof the membrane modules; and (c) one or more gas manifolds in flowcommunication with interior regions of the membrane modules and with theexterior of the pressure vessel.
 2. The system of claim 1 wherein eachplanar membrane module comprises a plurality of wafers having planarparallel surfaces, and wherein the pressure vessel is cylindrical andhas an axis that is parallel to some or all of the planar parallelsurfaces of the wafers.
 3. The system of claim 1 which further comprisesa flow containment duct disposed in the interior of the pressure vessel,wherein the flow containment duct surrounds the plurality of planar iontransport membrane modules and is in flow communication with any inletand any outlet of the pressure vessel.
 4. The system of claim 3 wherein(1) the one or more gas manifolds comprise an inlet manifold and anoutlet manifold; (2) the interior region of any planar membrane moduleis in flow communication with the inlet manifold via a secondary inletmanifold and is in flow communication with the outlet manifold via aprimary outlet manifold; and (3) within the flow containment duct, thesecondary inlet manifold and the primary outlet manifold of any planarmembrane module are combined to form a nested manifold.
 5. The system ofclaim 3 wherein the flow containment duct comprises anoxidation-resistant metal alloy containing iron and one or more elementsselected from the group consisting of nickel and chromium.
 6. The systemof claim 1 wherein the one or more gas manifolds are disposed in theinterior of the pressure vessel.
 7. The system of claim 1 wherein theone or more gas manifolds are disposed exterior to the pressure vessel.8. The system of claim 1 wherein the one or more gas manifolds areinsulated internally, externally, or internally and externally.
 9. Thesystem of claim 1 wherein at least two of the planar ion transportmembrane modules define a module axis, and wherein the pressure vesselis cylindrical and has an axis that is parallel to the module axis. 10.The system of claim 1 wherein at least two of the planar ion transportmembrane modules define a module axis, and wherein the pressure vesselis cylindrical and has an axis that is perpendicular to the module axis.11. The system of claim 1 which further comprises insulation disposed inthe interior of the pressure vessel.
 12. The system of claim 11 whereinthe insulation is disposed in a region between an interior surface ofthe pressure vessel and the membrane modules, wherein the insulationforms a cavity that surrounds the membrane modules and the cavity is inflow communication with any inlet and any outlet of the pressure vessel.13. The system of claim 12 wherein the insulation is in contact with theinterior surface of the pressure vessel.
 14. The system of claim 12wherein the insulation is not in contact with the interior surface ofthe pressure vessel.
 15. The system of claim 11 which further comprisesa flow containment duct disposed in the interior of the pressure vessel,wherein the planar ion transport membrane modules are disposed withinthe duct, and wherein the insulation is disposed between an interiorsurface of the pressure vessel and an exterior surface of the duct. 16.The system of claim 15 wherein the insulation (a) is in contact with theinterior surface of the pressure vessel and is not in contact with theexterior surface of the duct; or (b) is in contact with the interiorsurface of the pressure vessel and is in contact with the exteriorsurface of the duct; or (c) is not in contact with the interior surfaceof the pressure vessel and is not in contact with the exterior surfaceof the duct; or (d) is not in contact with the interior surface of thepressure vessel and is in contact with the exterior surface of the duct.17. The system of claim 11 which further comprises a flow containmentduct disposed in the interior of the pressure vessel and in flowcommunication with the inlet and outlet of the pressure vessel, whereinthe planar ion transport membrane modules are disposed within the duct,wherein the insulation is disposed between an interior surface of theduct and the membrane modules, and wherein the insulation forms a cavitythat surrounds the membrane modules and is in flow communication withany inlet and any outlet of the pressure vessel.
 18. The system of claim11 which further comprises insulation around the exterior of thepressure vessel.
 19. The system of claim 11 wherein the one or more gasmanifolds comprise metal and the ion transport modules comprise ceramic,wherein connections between the one or more gas manifolds and themodules comprise ceramic-to-metal seals, and wherein theceramic-to-metal seals are surrounded by the insulation.
 20. The systemof claim 11 wherein the insulation comprises one or more materialsselected from the group consisting of fibrous alumina, fibrous aluminasilicate, porous alumina, porous alumina silicate.
 21. The system ofclaim 11 wherein the insulation comprises one or more materials selectedfrom the group consisting of magnesium oxide, calcium oxide, copperoxide, calcium carbonate, sodium carbonate, strontium carbonate, zincoxide, strontium oxide, and alkaline-earth-containing perovskites. 22.The system of claim 1 which further comprises a guard bed disposedbetween any inlet of the pressure vessel and a first membrane module.23. The system of claim 22 wherein the guard bed contains one or morematerials selected from the group consisting of magnesium oxide, calciumoxide, copper oxide, calcium carbonate, sodium carbonate, strontiumcarbonate, zinc oxide, strontium oxide, and alkaline-earth-containingperovskites.
 24. The system of claim 1 which further comprises (a) oneor more additional pressure vessels, each having an interior, anexterior, an inlet, and an outlet; (b) a plurality of planar iontransport membrane modules disposed in the interior of each of the oneor more pressure vessels and arranged in series, each membrane modulecomprising mixed metal oxide ceramic material and having an interiorregion and an exterior region, wherein any inlet and any outlet of thepressure vessel are in flow communication with exterior regions of themembrane modules; and (c) one or more gas manifolds in flowcommunication with interior regions of the membrane modules and with theexterior of the pressure vessel; wherein at least two of the pressurevessels are arranged in series such that the outlet of one pressurevessel is in flow communication with the inlet of another pressurevessel.
 25. The system of claim 1 which further comprises (a) one ormore additional pressure vessels, each having an interior, an exterior,an inlet, and an outlet; (b) a plurality of planar ion transportmembrane modules disposed in the interior of each of the one or morepressure vessels and arranged in series, each membrane module comprisingmixed metal oxide ceramic material and having an interior region and anexterior region, wherein any inlet and any outlet of the pressure vesselare in flow communication with exterior regions of the membrane modules;and (c) one or more gas manifolds in flow communication with theinterior regions of the membrane modules and with the exterior of thepressure vessel; wherein at least two of the pressure vessels arearranged in parallel such that any inlet of one pressure vessel and anyinlet of another pressure vessel are in flow communication with a commonfeed conduit.
 26. The system of claim 1 which further comprises anadditional plurality of planar ion transport membrane modules disposedin the interior of the pressure vessel and arranged in series, whereinthe plurality of planar ion transport membrane modules and theadditional plurality of planar ion transport membrane modules lie onparallel axes.
 27. An ion transport membrane system comprising (a) apressure vessel having an interior, an exterior, an inlet, and anoutlet; (b) a plurality of planar ion transport membrane modulesdisposed in the interior of the pressure vessel and arranged in a seriesof banks of modules, each bank containing two or more modules inparallel, each membrane module comprising mixed metal oxide ceramicmaterial and having an interior region and an exterior region, whereinany inlet and any outlet of the pressure vessel are in flowcommunication with exterior regions of the membrane modules; and (c) oneor more gas manifolds in flow communication with interior regions of themembrane modules and with the exterior of the pressure vessel.
 28. Anion transport membrane system comprising (a) a pressure vessel having aninterior, an exterior, an inlet, and an outlet; (b) a plurality of iontransport membrane modules disposed in the interior of the pressurevessel and arranged in series, each membrane module comprising mixedmetal oxide ceramic material and having an interior region and anexterior region, wherein any inlet and any outlet of the pressure vesselare in flow communication with exterior regions of the membrane modules;and (c) one or more gas manifolds disposed in the interior of thepressure vessel and in flow communication with the interior regions ofthe membrane modules and with the exterior of the pressure vessel. 29.The ion transport membrane system of claim 28 which further comprises aplurality of additional wafer zones formed by the gas manifold shroudassembly, wherein the shroud assembly places the additional wafer zonesin series flow communication with one another, and wherein one of theadditional wafer zones is in flow communication with any outlet of thepressure vessel.
 30. A method for the recovery of oxygen from anoxygen-containing gas comprising (a) providing an ion transport membraneseparator system comprising (1) a pressure vessel having an interior, anexterior, an inlet, and an outlet; (2) a plurality of planar iontransport membrane modules disposed in the interior of the pressurevessel and arranged in series, each membrane module comprising mixedmetal oxide ceramic material and having an interior region and anexterior region, wherein any inlet and any outlet of the pressure vesselare in flow communication with exterior regions of the membrane modules;and (3) one or more gas manifolds in flow communication with theinterior regions of the membrane modules and with the exterior of thepressure vessel; (b) providing a heated, pressurized oxygen-containingfeed gas stream, introducing the feed gas stream via any pressure vesselinlet to the exterior regions of the membrane modules; and contactingthe feed gas stream with the mixed metal oxide ceramic material; (c)permeating oxygen ions through the mixed metal oxide ceramic material,recovering high purity oxygen gas product in the interior regions of themembrane modules, and withdrawing the high purity oxygen gas productfrom the interior regions of the membrane modules through the gasmanifolds to the exterior of the pressure vessel; and (d) withdrawing anoxygen-depleted oxygen-containing gas from any pressure vessel outlet.31. The method of claim 30 wherein the pressure of the oxygen-containingfeed gas is greater than the pressure of the high purity oxygen gasproduct.
 32. The method of claim 30 wherein the ion transport membraneseparator system further comprises a flow containment duct that has aninterior and an exterior and is disposed in the interior of the pressurevessel, and wherein the flow containment duct surrounds the plurality ofplanar ion transport membrane modules and is in flow communication withany inlet and any outlet of the pressure vessel such that theoxygen-containing feed gas passes through the interior of the flowcontainment duct.
 33. The method of claim 32 wherein the pressuredifferential between the interior and the exterior of the flowcontainment duct at any point between the inlet and outlet of thepressure vessel is maintained at a value equal to or greater than zero,and wherein the pressure in the interior of the duct is equal to orgreater than the pressure in the pressure vessel exterior to the duct.